[issue35859] Capture behavior depends on the order of an alternation

[Ma Lin]

Ma Lin <malincns at 163.com> added the comment:

You can `#define VERBOSE` in file `_sre.c`, it will print the engine's actual actions:

|02FAC684|02FC7402|MARK 0
...
|02FAC6BC|02FC7401|MARK 1

In my computer, 02FC7400 points to "ab", 02FC7401 points 'b' in "ab", 02FC7402 points to the end of "ab".

This capture group, begin at 02FC7402, end at 02FC7401. `begin > end` makes it return an empty string.

This seems a bug, the begin should at 02FC7400.

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue35859>
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